METHOD AND ARRANGEMENT FOR THE PAINTING TREATMENT OF MOTOR VEHICLE BODY SERIES

Description

[0001] The invention relates to a method for painting and drying motor vehicle bodies, in which bodies are immersed in tanks and provided with at least one coating, these coatings are subsequently cured, and after polishing and inspection as required, a hot wax sealant is applied. The invention further relates to an arrangement for carrying out the method.

[0002] Dip coating is an electrophoretic deposition process used primarily for coating vehicle parts in continuous operation. This electrochemical process involves immersing the workpiece, for example, a vehicle body, in an electrically conductive, water-based coating bath. A direct current field is applied between the workpiece and a counter electrode. Following the dip coating, thermal and / or optical treatment is immediately applied to cure (crosslink) the epoxy resin-based coating. This is typically done at temperatures between 150 and 200°C and / or using UV light.

[0003] Although cathodic dip coating is a long-established system in the automotive industry, there is still potential for improvement regarding cleanliness in such electrocoating processes, as described, for example, in DE 10 2011 018 562 A1, which provides a cleaning device for such electrocoating systems. This device uses an airflow to capture dust and / or paint particles. This improves the quality of the applied coating, and when implemented in the outlet of cathodic dip coating (KTL) dryers, it results in less waste, reduced cleaning effort, and a lower risk of smoldering fires with soot formation caused by paint particle buildup in the dryer.

[0004] The typical production processes for car body painting are described, for example, in DE 10 2018 116 488 A1, as follows: first, cathodic dip painting with subsequent drying; then, sealing of seams in the underbody of the respective car body with subsequent drying; a post-treatment of the cathodic dip painting in the so-called finish; and then, in a further process step, the application of a topcoat and subsequent drying. The topcoat also undergoes a post-treatment (topcoat finish), whereby, if necessary, a further subsequent process step involves cavity preservation, in which hot wax is applied to the underbody of the car body.

[0005] It is always necessary to transport the car bodies from one process station to the next, and possibly to intermediate storage areas, using suitable conveying equipment such as forklifts or similar devices. Since the car bodies receive their sales-ready surface coating after painting, and this coating is sensitive to dirt and especially mechanical damage, it is a known practice in automotive manufacturing to use temporary films for individual production steps. These films are applied to exposed areas of the car body before assembly and removed afterward. These protective measures are labor-intensive because the films currently used must be cut to the appropriate sizes, depending on the model and car part, and then applied manually. Therefore, these applications are labor-intensive and time-consuming, significantly increasing production costs.

[0006] Furthermore, peelable coatings or protective coatings are known to provide temporary surface protection for objects against dirt and damage. The dry coating film can then be easily peeled off the substrate. For example, Zuelch offers a peelable coating called Scheerolit, a copolymer that forms a high-quality, highly elastic coating. It is solvent-free, water-based, and can be applied to the object to be protected using an airless sprayer. Peelable coatings are frequently used to protect the walls of paint booths, allowing the paint overspray that inevitably accumulates and settles on the walls to be removed periodically along with the coating.

[0007] From US 2009 / 0 272 488 A1, a painting line is known comprising a painting station, a drying line and an underbody protection application area with heat treatment, wherein a peelable paint applicator is arranged in the direction of travel in front of the underbody protection application area.

[0008] A coating method and system for forming a protective layer is known from US 2007 / 0009656 A1, which describes an airless spraying system for applying the peelable coating.

[0009] From JP 2003 343978 A a drying oven for drying a peelable coating is known, in which the car bodies coated with the peelable coating are dried in a room with warm air of 90°C for three to four minutes.

[0010] German patent application DE 10 2014 211 259 A1 describes a method and device for cavity preservation in a vehicle body. It describes how the liquefied protective wax used for cavity sealing is applied to the body cavities at a temperature of approximately 100°C. These cavities have been preheated to a temperature of 60°C, for example, with warm air.

[0011] Lightfast coating materials, for example also as a transparent peelable lacquer, are known from DE 199 43 933 A1 and EP 1 072 652 A2, which are intended to serve as coatings for the protection of motor vehicles. After application, drying takes place at 20°C to 150°C.

[0012] The object of the invention is to protect the motor vehicle bodies, which have been painted ready for sale in a paint line, in a cost-effective manner for further handling and assembly, as well as to prevent contamination in the further process.

[0013] This problem is solved by a painting method according to claim 1 or in a painting arrangement according to claim 6.

[0014] By applying a peelable protective coating to the warming or still-warm bodywork during or immediately after the hot wax sealing process, a peelable coating is applied to the visible parts of the bodywork in parallel with the hot wax sealing process for the underbody and, if necessary, the body cavities. The heat generated by the hot wax sealing process is used to allow the peelable coating to dry as quickly as possible on the bodywork surface. An advantage of this method is that no separate heating energy is required, as the hot wax sealing process itself already heats the bodywork. Furthermore, no separate processing step is introduced, since the application of the peelable coating takes place immediately after or even during the hot wax sealing process.Since the hot wax sealant primarily covers the underbody of the car body and any cavities, the application of the peelable coating can be carried out in parallel with the hot wax sealant. This is because the exposed parts of the car body are not treated with hot wax, but these are precisely the parts that need protection with the peelable coating. Therefore, this additional step requires no separate thermal energy and no special temporal or spatial adjustments to the production line.

[0015] This is achieved by the device in which a peel-off coating applicator is arranged immediately downstream of the hot wax application area or in the direction of flow. The peel-off coating applicator can then apply the peel-off coating to the visible parts of the bodywork either parallel to or immediately after the hot wax sealing.

[0016] To achieve the fastest possible drying of the peelable coating on the car body, the surface temperature of the body during hot wax sealing is between 60°C and 150°C, particularly between 80°C and 120°C, and most preferably between 90°C and 100°C. Within this temperature range, the water content contained as a solvent in the peelable coating is rapidly released into the environment.

[0017] When the peelable coating is sprayed onto the car body, particularly using an airless sprayer, a uniform coating of the body is achieved. The spraying system, preferably an airless sprayer, can have nozzles mounted on robot heads that automatically perform the necessary spraying movements around the car body.

[0018] When warm air at 60°C to 100°C is passed over the car body coated with peelable paint, the drying process of the peelable paint applied to the warm car body is further accelerated by the warm airflow.

[0019] Preferably, the applied peelable coating dries on the warm bodywork within a drying time of 10 seconds to 5 minutes, particularly 20 seconds to 2 minutes. This means that the bodywork coated with the peelable coating is ready for further processing with a dried peelable coating, i.e., protected, as soon as it leaves the hot wax sealing area.

[0020] To protect the painted bodywork, a water-based and solvent-free peelable coating is provided for the peelable coating applicator.

[0021] An embodiment of the invention is described in detail below with reference to the accompanying drawing.

[0022] It shows: Fig. 1 schematically shows an arrangement for the painting treatment of motor vehicle bodies.

[0023] In Fig. 1 A schematic view of a paint line for automotive production is shown. X indicates the direction of travel (working direction) of the paint line. In the embodiment shown here, the car bodies are conveyed in the direction of travel X on an overhead conveyor 14. The painting process begins at a cleaning and passivation station 10, where the workpiece to be treated, in this case a car body W, is cleaned and passivated for subsequent painting. The car body W is then conveyed by the overhead conveyor 14 to the painting station 1 and immersed in a dip tank 11, in which a corrosion protection primer or filler is applied. The car body W is then intermediate-dried in a drying area 12. Finally, a base coat and topcoat are applied in a painting area 13. If necessary, further processing stations are provided, which are shown here in Fig. 1are not shown separately.

[0024] The coated car body W is then conveyed by the overhead conveyor 14 into a drying line 2. The drying line 2 contains a first heat source 21 and / or UV light sources 22 to thermally and / or optically cure the coating. The car body is then inspected and polished in an inspection and polishing area 3. Any improperly applied coatings are corrected, or the affected car bodies are rejected. The car body W is then conveyed into a hot wax application area 4, where a hot wax applicator 41 applies hot wax to the underbody and into cavities of the car body. Furthermore, a second heat source 42 is provided in the hot wax application area 4 to reach and maintain the temperature of 80°C to 100°C required for hot wax application during the application period.

[0025] Furthermore, a peelable coating applicator 5 is provided at this point, which has robot arms 52 with spray nozzles 51 arranged on them, which apply a peelable coating to the outer, visible parts of the body using an airless spraying process. In the embodiment shown here, a blower 53 is also assigned to the hot wax application area 4, which, if necessary, forces heated air along the body W sprayed with the peelable coating in order to accelerate the drying process of the applied peelable coating.

[0026] At the end of the hot wax application area 4, the fully painted body shell, coated with hot wax on the underbody and cavities and with peelable lacquer in the visible areas, is then discharged to a discharge area 50. From here, the body shell can be sent to further processing steps, in particular for further assembly.

[0027] The vehicle body is protected against contamination and mechanical damage by a peelable coating. This removable protective coating can partially eliminate the need for subsequent body wraps, as the coating itself provides sufficient protection. This eliminates the need for time-consuming, custom-cut films that would otherwise have to be applied by hand, which is advantageous in terms of both production costs and environmental impact. This peelable coating can remain on the vehicle throughout the entire manufacturing process, from the production line to handover, including during transport. The coating can therefore remain on the vehicle for anywhere from several hours to several months. Reference symbol list

[0028] 1. Paint station 10. Cleaning / passivation position 11. Immersion tank 12. Drying area 13. Paint area 14. Ceiling conveyor 2 Drying line 21 First heat source 22 UV light source 3. Inspection and polishing area 4 Hot wax application area 41 Hot wax applicator 42 Second heat source 5 Peel-off paint applicator 50 Dispensing area 51 Spray nozzle 52 Robot arm 53 Blower X Flow direction W Workpiece, body

Claims

1. Method for painting and drying motor vehicle bodies, in which vehicle bodies (W) are provided with at least one coating in a painting station (1), this coating or these coatings are then cured and, after polishing and inspection as required, a hot wax seal is applied, characterised in that during or immediately after the hot wax sealing, a peelable coating is applied to the warming or still warm vehicle body (W) as a peelable protective coating.

2. Method according to claim 1, characterised in that the vehicle body (W) has a surface temperature of 60°C to 150°C, in particular 80°C to 120°C, and most preferably 90°C to 100°C during hot wax sealing.

3. Method according to claim 1 or 2, characterised in that the peelable coating is sprayed onto the vehicle body (W), in particular using the airless method.

4. Method according to claim 1, 2 or 3, characterised in that hot air at 60°C to 100°C is directed over the vehicle body (W) coated with the peelable paint.

5. Method according to one of the preceding claims, characterised in that the applied peelable coating dries on the warm vehicle body (W) in a drying time of 10 seconds to 5 minutes, in particular 20 seconds to 2 minutes.

6. Arrangement for carrying out the method according to one of the preceding claims, with components following one another in the direction of flow, namely a painting station (1), a drying line (2) and a hot wax application area (4) with heat treatment, characterised in that a peelable coating applicator (5) is arranged in the hot wax application area (4) or immediately downstream of the hot wax application area (4).

7. Arrangement according to claim 6, characterised in that the peelable coating applicator (5) is a spraying system, preferably an airless spraying system.

8. Arrangement according to claim 6 or 7, characterised in that a warm air blower (53) is provided, the air flow of which is directed towards the vehicle body (W) behind the peelable coating applicator (5) in the direction of travel (X).

9. Arrangement according to claim 6 or 7, characterised in that a water-dilutable and solvent-free peelable lacquer is provided for the peelable coating applicator (5).